The exchange coupling and spin waves in metallic magnets: removal of the long-wave approximation

TL;DR

This paper introduces a new computational approach that removes the long-wave approximation in studying exchange coupling and spin waves in metallic magnets, improving accuracy for itinerant electron systems.

Contribution

It develops a method combining inverse susceptibility and multiple scattering theory to better describe exchange interactions and spin wave spectra in metals like Fe, Ni, and Gd.

Findings

Enhanced accuracy in exchange coupling calculations

Improved spin wave spectrum predictions at large wave vectors

Better description of magnetic short-range order effects

Abstract

A well-known connection between the magnetic susceptibility and the effective exchange parameter is analyzed. It is shown that all current computational schemes use a long-wave approximation which is suitable only for localized moments systems. A corresponding smallness parameter is derived in real and recipical space. General 'inverse susceptibility' approach is combined with a multiple scattering theory and applied for the studies of elementary metals Fe, Ni and Gd. It is shown that the proposed approach significantly improves the description of the exchange coupling between nearest atoms, the spin wave spectrum at large wave vectors for the itinerant degrees of freedom in metallic magnets. A consistent usage of this method leads to the proper description of magnetic short-range order effects.